Blackberry doesn't adjust your clock based on the physical location of the device. Its based on the time zone you've set on the device. As are your appointments.
Let's say that your device is based on Eastern Time, but you're in the Central time zone. You've got an appointment at noon CST. You would need to enter that appointment in as Eastern time (1pm).
Alternatively, change the time zone as you travel. When you arrive in a different time zone, set a reminder to manually change the zone. Don't manually adjust the clock--this is where the confusion lies....time zone adjustment only.